There is Taratamya or gradation of souls in this universe, and every soul has its own place in this hierarchy. This can be seen in every object on this planet. Take the rocks for instance – there are several gradations in them, right from the diamond at the top to a small pebble on the beach. The same is the case with the humans too and moreover people tend to find their soul mates from the more or less the same gradation as they are. In fact, it is no different among gods and goddesses too.
Lord Krishna, who is an incarnation of Vishnu, is often described as HariSarvothama(i.e the supreme being), and is considered as 8th Rasa known as parama parardhya rasatama in chandogya Upanishad. Goddess Lakshmi, who is none other than Rukmini , falls very next in the hirerachy of supremacy as 7th Rasa known as parama parardhi rasatama and therefore has the authority to destroy Lord Shiva at the time of Pralaya (Doomsday) as mentioned in chandogya upanishad.
Lakshmi-The Goddess of wealth, married Lord Vishnu who has no material possessions, because there is nothing outside of him and there is nothing for him to possess. And it is for the same reason that his devotees abandon everything to attain him. They are worthy of his association and not those who are attached with materialistic life.
Goddess Lakshmi has responsibility to take care of 14 worlds, involves cleaning them too,which includes mount meru which has tremendous gold and is 16000 yojna (one yojna=12-15 Kms) below and 84000 yojna above. It is said that 33 crore Gods and Goddess who are nurtured by her,at the same time to punish them, if they indulge in any kind of sin. As every women in her household takes care of milk, curd,etc and yet sometimes is not capable preventing them from spoiling. But Goddess lakshmi cannot afford to do this and has to protect sea of milk, curd, ghee and sugarcane juice present in vaikuntha and she is proficient in her work and never fails. Lord Krishna looks at her and she looks at world and her work is done. It is as easy as that for her.
Lord Krishna never married anyone but Goddess Lakshmi, and he is never in contact with anyone one else apart from her. She is present in the jewellery he wears, the flute he plays and the weapons he uses and just about anything and everything. He never touches a thing in which she is not present. He is never angry on her because, they can never think differently, as they are like one and the same. Goddess Lakshmi’s love and devotion towards her husband is infinite and unconditional. Lord Krishna will embrace her with love, even the situation demands a pralaya(apocalypse) from him. This exemplifies their love towards each other and significance of taratamya(gradation) in the universe.